PhD Theses at KOM

Christian Reuter

Monday July 25, 2016

English abstract:

Video games are not only a growing business field, but also provide interesting research opportunities. In particular, collaborative multiplayer games have become increasingly popular with players, developers and researchers alike. These games offer players the opportunity to tackle difficult challenges together instead of competing against each other. Collaboration within a game not only increases player interest and developer revenue, research has also shown that it can have positive effects on the players’ social skills.The rise of collaborative games, however, also has a downside. As more developers create this kind of game, instances in which players complain about the collaborative elements being implemented halfheartedly are becoming more and more frequent. At least in part, this can be attributed to the fact that developing collaborative multiplayer games introduces unique challenges to the game development process. The players must not only get enough opportunities to interact with each other in a meaningful way, but it is also essential that their contributions are similar. Moreover, testing the game becomes more difficult due to a higher number of testers required. But even when there are enough testers, the complexity of the state space grows exponentially with each new player. This means that human testers are often unable to test every combination of events. These aspects make it much harder to develop collaborative games, especially for small and inexperienced teams.Although these issues are well known, the current state of the art is only partially able to solve them. For example, there are guidelines on how to develop collaborative games - but these only give general ideas. Therefore, they are not always directly implementable, especially for developers that are new to multiplayer development. This thesis aims at supporting those developers by conceptualizing an authoring environment that addresses these issues. Its overall concept consists of three steps or four modules: Game design patterns as player interaction templates (1), a formal analysis concerning structural errors (2a) and collaborative balancing (2b) as well as a rapid prototyping environment (3).To help developers with the initial design, a number of well-received player interactions, which can be seen as the central element of a collaborative game, is gathered. These interactions are described using the well-known format of game design patterns. In order to make the patterns more user-friendly, the format is extended with properties specific to collaborative interaction. For example, one property describes whether the players must be close to each other in order to trigger the interaction. Following this, a representative selection of the patterns is used to develop a game, in which collaboration can be switched off. This game is evaluated in a user study later. Here, the outcomes have shown that the interactions are well received by the players.If combined in the wrong way, however, these interactions can cause structural issues such as deadlock situations, i.e. a state from which the game can no longer be completed. In order to detect such problems, verification algorithms can be used. Those require the transformation of the game into a formal model. As such, colored petri nets are chosen, since they can model concurrent actions by multiple players. Since developers cannot usually be expected to create such a model by themselves, an automated transformation approach is devised. For that, rules between each element of the underlying game model and the elements of a colored petri net are defined. Additionally, optimization rules are developed to mitigate the state space explosion when verifying complex games. These rules use knowledge about the game model in order to reduce the complexity of the resulting petri net. Evaluations with both existing games and synthetic examples confirm that such a verification approach is viable for smaller games.Whether the game involves all players on an equal basis can be checked in tandem to this. However, a novel definition for balancing in collaborative games needs to be created first, as the related work only examines balancing from a competitive perspective. Based on this definition, concrete measurements to indicate disparities between the players are devised. As the games’ complexity and the players’ influence on the course of the game prevent exact measurements, an approximation approach is instead developed. Similar to the structural verification, an evaluation shows that this approach works for smaller games.Finally, a rapid prototyping environment is designed, which allows a single developer to test games designed for up to four players. For this, visual and audio information for separate players is made both observable and, at the same time, clearly attributable. Additionally, simultaneous player actions can be simulated by using a record and replay approach.By implementing and evaluating these modules, this work is able to show how development issues that are specific to collaborative multiplayer games can be addressed. Using these modules can therefore reduce the effort involved in developing collaborative multiplayer games.